configuration is similar to the PPPoE configuration. The difference between the two configurations is shown in the configuration outputs illustrated in the Figure :
Content 2.6 Configuring the CPE as the PPPoE or PPPoA Client 2.6.11 Configuring a DSL ATM Interface Figures and show the steps you use to configure a DSL ATM interface. Use the dsl operating-mode auto interface configuration command to specify that the router automatically detects the DSL modulation that the service provider is using and sets the DSL modulation to match. An incompatible DSL modulation configuration can result in failure to establish a DSL connection to the DSLAM of the service provider. Use the pvc interface configuration command to set the virtual path identifier/virtual channel identifier (VPI/VCI) that is used by the DSL service provider, as shown in the pvc Parameters table. Settings for the VPI/VCI value on the Cisco router must match the configuration on the DSLAM of the service provider switch configuration. ATM uses the VPI/VCI to identify an ATM VC. pvc Parameters
Parameter Description Vpi VPI from the service provider Vci VCI from the service provider The encapsulation method must correspond with the method configured on the aggregation router. The Encapsulation Commands table shows the available commands.
Encapsulation Commands
Command Description encapsulation aal5mux ppp dialer Sets the encapsulation for PPPoA, which uses AAL5 in the MUX mode dialer pool-member number Links the ATM interface to a dialer interface Use the dialer pool-member command to specify which dialer interfaces can use the ATM physical interface on the Cisco router. Figure shows an example of a complete PPPoA configuration. The example presents the complete PPPoA configuration with PAT, DHCP services, MTU adjustments, and static default routing.
Content 2.7 Troubleshooting Broadband ADSL Configurations 2.7.1 Troubleshooting Layers 1, 2, and 3 ADSL service problems can reside at Layer 1, Layer 2, or Layer 3. Troubleshooting should start by determining which ADSL service layer is failing. To determine which layer has a problem, use a bottom-up approach; that is, start troubleshooting at Layer 1 and move to subsequent layers as required. Figure illustrates this approach.
Content 2.7 Troubleshooting Broadband ADSL Configurations 2.7.2 Determine Whether the Router Is Properly Trained to the DSLAM Start troubleshooting Layer 1 by verifying whether a Cisco Systems CPE router is trained to the DSLAM in the CO by using the show dsl interface atm command. When a router is successfully trained to the DSLAM, the modem status field has the value Showtime. Along with that value, the command also displays the upstream and downstream speed in kbps (in the row Speed, the Interleave or Fast columns will have a nonzero value). Figure is an example of the output from a properly trained modem. If the modem and router are properly trained, move troubleshooting efforts to Layer 2. When the router is not properly trained, as shown in the following output, the problem is at Layer 1, and a solution needs to be found at this layer. Router#show dsl interface atm 0
Line not activated: displaying cached data from last activation
Log file of training sequence:
<...rest of the output omitted...>
Content 2.7 Troubleshooting Broadband ADSL Configurations 2.7.3 Troubleshooting Layer 1 Issues You can monitor the status of the ATM interface on the router by checking the status of the Carrier Detect (CD) light on the router’s interface panel: Next, use the show interface atm privilege level command from the enable mode of the router to check the status of the ATM interface on the router. This command appears in Figure . If the ATM interface status is down and the line protocol is down, the router is not seeing a carrier on the ADSL line. Such a status usually indicates two possible issues: The Cisco router uses a standard RJ-11 cable to provide the ADSL connection to the wall jack. The center pair of pins on the RJ-11 cable carries the ADSL signal (pins 3 and 4 on a 6-pin cable, or pins 2 and 3 on a 4-pin cable). If the wall jack is using the correct pins, and the ATM interface is still down and the line protocol is down, replace the RJ-11 cable between the DSL port and the wall jack. If the interface is still down and the line protocol is down after you have replaced the RJ-11 cable, contact the service provider to verify that ADSL service has been enabled on the wall jack you are using. The show interface atm command also shows whether the interface is administratively disabled. If such a case exists, enable the interface by using the no shutdown command under the interface configuration mode.
Content 2.7 Troubleshooting Broadband ADSL Configurations 2.7.4 Determining the Correct DSL Operating Mode If everything that you have checked up to now in the Layer 1 troubleshooting procedure is verified and is operating properly, the next step is to ensure that the correct DSL operating mode is being used. Check with the service provider whether the DSLAM supports the particular DSL chipset (for example, Alcatel) and the configured modulation method of the deployed Cisco CPE DSL router. If the DSL modulation being used by the service provider is unknown, Cisco recommends using the default auto operating mode to autodetect the modulation type. Run the auto operating mode using this command (see the dsl operating-mode Parameters table for details): dsl operating-mode {auto | ansi-dmt | itu-dmt | splitterless} dsl operating-mode Parameters
Parameter Description auto Configures the ADSL line after auto negotiating with the DSLAM located at the CO; this is the default operating mode ansi-dmt Configures the ADSL line to use the ANSI T1.413 Issue 2 mode itu-dmt Configures the ADSL line to use the G.992.1 mode splitterless Configures the ADSL line to use the G.992.2 (G.lite) mode If problems persist and the router has been properly configured, proceed to Layer 2 examination and troubleshooting.
Content 2.7 Troubleshooting Broadband ADSL Configurations 2.7.5 Troubleshooting Layer 2 Issues After establishing that Layer 1 is operating correctly, the troubleshooting can continue at Layer 2. First, check whether a permanent virtual circuit (PVC) is configured at the DSLAM by using the ping atm interface atm command. This command sends Operation, Administration, and Maintenance (OAM) F5 loopback packets to the DSLAM. A successful ping designates that a PVC is configured at the DSLAM. Next, check whether the correct VPI/VCI values are configured on the router, by using the debug atm events command. The output shows the VPI/VCI values that the DSLAM expects. During the debug process, use another working Internet connection and begin to ping the static IP address assigned by your Internet service provider